When a rectangular wire used for a coil of a rotating electric machine is subjected to an edgewise-bending process (hereinafter, simply referred to as a bending process), the sheet thickness (the length of a short side of a rectangular cross section perpendicular to a longitudinal direction of the rectangular wire, the same applies hereinafter) of a processed part becomes greater than that of an element wire. At the part where the sheet thickness increases, layers of a rectangular wire stacked as a coil interfere with each other, thereby causing reduction in a space factor of the coil. Considering this, as a method for suppressing increase in the sheet thickness of a rectangular wire, a technique is proposed in which a surface formed by a long side of a rectangular cross section of the rectangular wire is pressed by a deformation mechanism to deform in advance the rectangular wire so that the sheet thickness thereof is decreased, and then a bending process is performed (for example, Patent Document 1).